Non-contact strip coil linear footage measuring apparatus and method

ABSTRACT

Method and apparatus for very accurately determining the length of strip coils, such as hot or cold rolled steel strip, without contacting the strip.

United States Patent 1191 Slagley et al.

1 1 Jan. 9, 1973 [54] NON-CONTACT STRIP COIL LINEAR FOOTAGE MEASURING APPARATUS AND METHOD [75] Inventors: William E. Slagley, Columbus, Ohio;

Gerald R. Seiiert, Calumet City; Edmund J. Valonis, l-lomewood, both of 111.

[73] Assignee: Inland Steel Company, Chicago, Ill.

[22] Filed: April 29, 1971 [21] Appl. No.: 138,633

[52] US. Cl ..235/l5l.32, 235/92 DN, 242/184,

250/219 LG, 250/219 S [51] Int. Cl ..G06f'l5/46 [58] Field of Search ..235/151.3, 151.32, 92 DN; 242/7551, 75.52, 184,185;250/219 WE,

219 LG, 219 S; 318/6 [56] References Cited UNITED STATES PATENTS,

COMPUTER PRINTER DISPLAY 3,315,907 4/1967 Jura ..242/185 X 3,519,831 7/1970 Tetzner.... ..250/219 S 3,172,208 3/1965 Lowy ..235/151.32 UX 3,406,601 10/1968 Clifford ....235/151.32 X 3,553,992 1/1971 l larbaughm. ..242/75.51 X 3,564,219 2/1971 Mutziger ..235/151.32 X 3,600,562 8/1971 Dinicolantonio et al. ..235/151.32

OTHER PUBLICATIONS CRC Handbook of Tables for Mathematics, The

Chemical Rubber Co., Fourth Edition, Copyright Primary Examiner-Eugene G. Botz Assistant Examinerlerry Smith Attorney-Merriam, Marshall, Shapiro & Klose 57 ABSTRACT Method and apparatus for very accurately determining the length of strip coils, such as hot or cold rolled steel strip, without contacting the strip.

12 Claims, 4 Drawing Figures 57 67 START STOP COUNT CORRECT RESET SIG.

| 1 DISPLAY I LAP COUNT L. l

PATENTEDJMI 9 I873 3. 7 1 0 O84 SHEET 1 [IF 2 F l G. l

RADIUS START STOP IN Pu lgER S'GNAL gfm 233$? RESET SIG.

. PULSE SHAPER F l G. 2

INVENTORS WILL/AM E SLAGLEY [5 GERALD R. SE/FERT EDMUND J. E ALON/S BY Z-bk ATTORNEYS PATENTEU MN 91975 3.710.084

SHEET 2 OF 2 F IG.3

ATTORNEYS- NON-CONTACT STRIP COIL LINEAR FOOTAGE MEASURING APPARATUS AND METHOD The present invention relates to a system for determining the length of a strip coil. In general, it concerns.

method and apparatus for very accurately determining the linear footage of a strip coil without contacting the strip during the coiling or uncoiling process.

BACKGROUND In the manufacture and sale of strip coil products, for example hot and cold rolled steel strip or aluminum strip, plastic, paper, or any other coiled product, it is important to know the exact length of strip in each coil. Errors in determining the exact length present problems of serious economic and commercial concern to both the manufacturers and the users of strip coils. As a result, various methods and apparatus have been employed heretofore in attempts to accurately determine the length of strip coils.

Strip coils are typically manufactured by a process in which a strip of material, for example, cold rolled steel strip exiting from a mill, is wound or coiled around a rotating or revolving mandrel, forming. layers of substantially concentric circles. Generally, before reaching the mandrel, the strip contacts one or more bridle rolls which support, guide and/or provide power to move the strip towards the mandrel.

In the prior art, various methods and apparatus for measuring the length of strip coils have been disclosed and employed. In general, prior art systems may be classified as either contact of non-contact systems. In contact systems, the strip coil length determination depends upon mechanically contacting either the strip,

, the mandrel, or a bridle roll during the coiling operation. In non-contact systems, the determination of the strip coil length is accomplished without mechanically contacting the strip, the mandrel, or the bridle rolls during the coiling operation.

Prior art contact systems present several disadvantages. For example, one commonly employed contact device employs a low inertia measuring wheel which contacts the moving strip during the coiling operation, causing the measuring wheel to rotate. The number of rotations is a functionof the length of the strip contacted. Such devices produce inaccurate results due to wear of the measurement wheel or slippage of the measurement wheel due to fast acceleration or deceleration of the strip or as a result of oil on the strip. Moreover, low inertia measuring wheels frequently mark the strip and are easily damaged due to their necessarily frail construction.

Low inertia measuring wheels used in contact with a bridle roll instead of the strip eliminate some of the above disadvantages, but these latter systems present other disadvantages. For example, slippage between the strip and the bridle roll with which the measuring wheel is in contact introduces error as does any wear in the diameter of the bridle roll.

Measuring wheels or measuring rolls also have a disadvantage in that it is necessary for the strip to pass over a measuring roll or back up roll. In doing so, the strip forms an arc of a circle with the inner surface in contact with the roll and in compression. The surface away from the roll is in tension. The true length of the strip is on the unstressed neutral axis. Thus, the measuring wheel or roll must measure either the length of the compressed inner surface or the stretched outer surface. The error introduced due to this phenomenon depends on the angle of wrap, the roll diameter, and the strip thickness. For example, material l/l6 inch thick wrapped over a 12 inch roll will have its two surfaces stretched or compressed to a length 0.52 percent different from the length along the neutral axis.

Prior art non-contact systems also are not entirely satisfactory and generally do not provide very accurate determinations of strip coil length. For example, one such non-contact system employs the use of X-rays to measure strip thickness and uses this measurement, together with a measurement of the mandrel revolutions, to calculate the length of the strip of the coil. In this system, the X-rays can only measure the strip thickness to within about 3 percent. Such a degree or error can result in an error of about 3 percent in the total length of the strip, which is an unacceptable, inaccurate determination. Furthermore, if the strip is not tightly and uniformly wound, this method cannot compensate for spacing between laps and particularly variation in said spacing.

DESCRIPTION OF INVENTION The present invention provides an improved system for very accurately determining the length of a strip coil. Accuracies better than 0.5 percent and generally better than 0.1 percent are obtained.

Briefly, and in its broadest aspects the present invention involves determining the length of a strip coil by determining the arc length of strip as it is wound on the mandrel while the mandrel rotates through a known angle. The total strip length is then equal to the summation of all of the arc lengths. Each arc length is equal to r6 where r is the radius of the lap being coiled, and 6 is the angle of the are measured in radians.

I In a preferred embodiment of the present invention each lap is divided into ten are segments, so that 0 is always 21r/l0 radians. Each time the mandrel rotates through the angle 0 the radius r is measured in feet, the segment length r0 is computed, and the arc length is added to a totallizing register.

The present invention will be better understood by reference to the accompanying drawing in which:

FIG. 1 is a block diagram;

FIG. 2 is a perspective view of a strip coil being formed and shows a pulser suitable for use in the invention;

FIGS. 3 and 4 are both side views of a strip coil being formed and show alternate coil radius signal devices each suitable for use in the invention.

FIG. 1 indicates the various means necessary to compute the total footage wound on a mandrel (not shown). The 6 pulser 1 is a device that provides an electrical pulse each time the mandrel rotates 217/10 radians, or one-tenth revolution. This will be further described hereafter in connection with FIG. 2. The pulse is shaped by a pulse shaper 2, such as a Schmitt trigger. Each shaped pulse is used to direct computer 3 to perform an arc length calculation. Coil radius signal device 4, described hereafter in connection with FIG. 3 and FIG. 4, continuously measures the radius in feet of the lap being coiled and feeds a digital signal to computer 3. With each 0 pulse a new r0 is computed by computer 3 and this arc length is added to a totallizing' register contained in computer 3.-The footage total, to' the nearest one-tenth foot, can be displayed with a digital readout device 8, and/or the footage total may be printed out on paper tape with printer 7.

Since the mandrel may be moved before the strip is threaded onto the mandrel or after the strip is cut off, it is desirable toalso have a start count signal 5, and a stop count signal 6. Either of these signals maybe initiated by a pushbutton. However, it is desirable to i make these signals automatic by using relay contacts using the formula:

associated with other operations of the mandrel. For

example, if themandrel is equipped with a gripper slot, closing the gripper slot on the strip could be the action used as thestart count signal. Thus,.a contact on the gripper slot actuating relay could be used to start the count. If the mandrel is equipped with a belt-wrapper,

retraction of the belt-wrapper after a coil is.started could be used to start the count.

The stop count signal 6 wound most-commonly come from actuating a shear or other such device that cuts the strip before .the'coil. When the stop count signal is received by computer 3 it wouldignore shaped pulses and radius signals until receiving the next start-count signal. Computer 3 would then go through a set of preprogrammedf functions including making corrections to the total footage, actuating printer 7 (and/or other display means) and resetting.

Several corrections to 'the footage total may be desirable/For example, since the arc length stops when the shear is actuated, the strip length between the shear and coil is preferably added automatically. This is a constant footage which canbe measured once and.

thereafter included in the pre-programmed functions.

Another desirable correction is referred to herein as the neutral axiscorrection. Since the radius measuring device to be described hereafter always measures the outside radius of each lap it is measuring a radius halfa strip thickness longer than the radius on the unstressed neutral axis ofeach lap. Over an entire coil this adds a length equal to'n'times the coil wall thickness. To be very accurate, computer 3 can be programmed, to subtractthis amount of footage by computing 1r(r,,-r,)

' where r.) is the radius of the outsidelap and n is the I radius of the .mandrel. .This footage is then automatically subtracted from the previously calculated total before. theprint-out'is initiated.

Ifa beltwrapper is used an additional correction may be desirable to account for the footage which is wound on the mandrel before the belt wrapper is retracted. For example, the operator may win three full wraps on the mandrel; before pressing the button which retracts the belt wrapper and starts the footage count. In this Length= 10+ YOD)/2 (1r) (N),

where ID is the inside diameter, of the coil in feet, 0D is the outside diameter of the coil in feet and N is the number of laps. No correction is required when using this formula because the average lap diameter used gives the length along'the unstressed neutral axis of each lap.

The 0 pulser l is better understood by referring to FIG. 2. In the drawing there. is shown a metal strip 10 being wound around a mandrel 11 to form a strip coil 12. Associated with the mandrelll is 0 pulser 1 comprising light interrupting means 14, light source 15, and photocell l6. Light interrupting 7 means 14, which is secured to and rotates with mandrel 1 1 is provided with ten flags 17 which periodically interrupt the lightbeam from light source15. Each such interruption serves as a pulse which is shaped e.g., by a Schmitt trigger-(not shown) .and fed to computer 3. The light interrupting means 14 may be cut from any opaque material and fastened to the mandrel drive shaft coupling. The cutting need not be precise as long as ten flags, approximately equispaced, are provided The coil radius signal device employed in the present invention may be any one of several types. Two types are shown in' FIG. 3 and FIG. 4.

FIG. 3 shows a device employing low pressure air to sense the body of the coil. Low pressure .air from a header 20 is fed to tubing 21 in the center ofa wand 22. Air flows through a constricting orifice 23 and through a nozzle 24 against-the outer lap ofa coil 25 The proximity of'coil 25 to nozzle 24 determines the back pressure in the tubing between orifice 23 and nozzle 24. If nozzle 24 were to touch coil 25, pressure between orifice 23 and nozzle 24 would be at a maximum. Pressure is'transmitted to an outer tube 2 6 and tea pneumatic amplifier 27. Pneumatic amplifier 27 uses energy from supply header 20. and provides an input signal to a case the computer can beprogrammed to add 611' r number. of 0 pulses as theyjare received during. the" fo'rming of each coil-. Lap count display-9 may be used as a check on the hardware of the system. If the strip is relatively heavy material, approximately Ill 6 inch thick or heavier, it is possible to-count the laps. manually after the coil is off the mandrel. It is also possibleto get a check on the complete system by meahydraulic amplifier 28 Hydraulic amplifier 28 uses high pressure oil from a supply 29 to position a piston 30 within a cylinder 31. The pneumatic, amplifier 27 and hydraulic amplifier 28 are so designed that the position of wand 22 will follow the outer lap of coil 25 as coil 25 builds up. Nozzle 24 will remain a small and predictable distance away from the outer lap of the coil. This is the same principle as is used-in a flapper type pneumatic regulator. I

Fixed to'wand 22 and moving with itisrack 32. The teeth of rack 32 engagea pinion 33 which drives a shaft position encoder 34. The encoder 34 feeds a signal to a digital integrator 35. The output of integrator 35 is a digital signal corresponding to the coil radius in feet.

Modifications to the above coilradius device could be employed. For example, the proximity of coil 25 could be sensed using an electrical induction or capacitance-device and wand 22 could be electrically driven instead of hydraulically driven. i

A second type of coil radius signal device is shown in FIG. 4. Thisdevice has the, advantage that it can be located several feet away from the moving coil. As a strip 40 is wound into a coil 41 on a mandrel 42, a

eye 43 contains several photocells which are in a bridge network that is balanced only when half the photoelectric eye is exposed to light. The photoelectric eye 43 feeds it signal through a festooned wire 45 to a servoamplifier 46. The output of servoamplifier 46 is used to drive a servomotor 47. Servomotor 47 is coupled to a worm 48. A traveling nut 49 is driven along worm 48 and kept from turning by a guide rod 50. The servo system has zero error and zero driving torque when the traveling nut is so positioned that the photoelectric eye is on the edge of the coil. Also coupled to servomotor 47 is a shaft position encoder 51. The shaft position encoder 51 feeds s signal to a digital integrator 52. The

output of integrator 52 is a digital signal corresponding to the coil radius in feet.

When removing the coil from mandrel 42 the entire servo support assembly 53 can be swung out of the way, pivoting on a pin 54.

From the above, it is apparent that the method and apparatus of the present invention offer several advantages over prior art systems. For example, very accurate length determinations can be made. Neither wear of rolls, acceleration or deceleration of the strip, nor the presence or absence of foreign substance, e.g., oil, on the strip, cause error in the length determination. In addition, with the present invention, coils can be tailor made to very specific lengths since length measurements can be reported concurrently with forming the coil. Moreover, the present apparatus does not produce marks on the strip, and can be located out of the path of the strip where it is less likely to be damaged. I

lt should be apparent that the present invention can also be used in paying out a coil from an unwinding reel into'a shearing unit or into another process.

While the present invention has been described with reference to the accompanying drawings and to'certain examples, various modification will be apparent to those skilled in the art.

What is claimed is:

l. A method for determining the length of a strip coil during its coiling or uncoiling on a mandrel, said method comprising: (a) continuously measuring the outside radius of the coil, without mechanically contacting the strip, and generating a signal, r, proportional thereto; (b) generating a pulse, 6, each time said mandrel rotates a predetermined amount; (c) calculating each arc length, Or, of the coil and; (d) summing all said arc lengths to thereby provide the length of the strip coil.

' 2. A method according to claim 1 wherein said predetermined amount is 21r/1O radians.

3. A method in accordance with claim 1 wherein the sum obtained in step (d) is adjusted by a neutral axis correction factor.

4. A method in accordance with claim 1 wherein the sum obtained in step (d) is adjusted by a predetermined footage which is. wound on the mandrel before the footage counting is initiated.

5. A method in accordance with claim 1 wherein the 'method is initiated in response to the start of mandrel rotation.

6. A method in accordance with claim 1 wherein step (cllis stopped in response to shearing of said strip.

. Apparatus for accurately determining the length of a strip coil during its coiling or uncoiling on a mandrel, said apparatus comprising; pulser means for generating a pulse, 0, each time said mandrel rotates a predetermined amount; coil radius signal means for continuously measuring the outside radius of said coil without mechanically contacting the strip and generating a signal, r, proportional thereto; and computer means for calculating each arc length, 6r, of said coil and further for totaling all said are lengths.

8. Apparatus as defined by claim 7 wherein said pulser means generates an electrical pulse.

9. Apparatus as defined by claim 7 wherein said coil radius signal means comprise means for sensing the outside radius of said coil with low pressure air.

10. Apparatus as defined by claim 7 wherein said coil radius signal means comprise a light source and photoelectrical eye means for sensing the outside radius of said coil.

11. Apparatus as defined by claim 7 which includes starting means for initiating the operation of said pulser means and said coil radius signal means in response to the start of mandrel rotation.

12. Apparatus as defined by claim 7 including shear actuated stop means.

w-wso I UNKTED STATES PATENT OFFIQE ERTlFlCATE QURREQTEN Patent No. 3,710,084 Dated January 9, 1973 lnventofls) WILLIAM E... SLAGLEY, GERALD R6 SEIFER'I, and EDMUND- J.

VALONIS It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

At Col umn 2, line 18 delete ""or insert -of;

At Column 3, line 21 delete "wound" insert would At Column 3 line 53 delete "win" insert w ind-- I At Column 5, line 4 delete-"it" inSert --its-.

Sigried and sealed this 29th day of May 1973.

. (SEAL) Attest: I

EDWARD MV.FLETCHER,JR. ROBERT GOTTSCHALK Attesting-Officer I Commissioner of Patents 

1. A method for determining the length of a strip coil during its coiling or uncoiling on a mandrel, said method comprising: (a) continuously measuring the outside radius of the coil, without mechanically contacting the strip, and generating a signal, r, proportional thereto; (b) generating a pulse, theta , each time said mandrel rotates a predetermined amount; (c) calculating each arc length, theta r, of the coil and; (d) summing all said arc lengths to thereby provide the length of the strip coil.
 2. A method according to claim 1 wherein said predetermined amount is 2 pi /10 radians.
 3. A method in accordance with claim 1 wherein the sum obtained in step (d) is adjusted by a neutral axis correction factor.
 4. A method in accordance with claim 1 wherein the sum obtained in step (d) is adjusted by a predetermined footage which is wound on the mandrel before the footage counting is initiated.
 5. A method in accordance with claim 1 wherein the method is initiated in response to the start of mandrel rotation.
 6. A method in accordance with claim 1 wherein step (c) is stopped in response to shearing of said strip.
 7. Apparatus for accurately determining the length of a strip coil during its coiling or uncoiling on a mandrel, said apparatus comprising; pulser means for generating a pulse, theta , each time said mandrel rotates a predetermined amount; coil radius signal means for continuously measuring the outside radius of said coil without mechanically contacting the strip and generating a signal, r, proportional thereto; and computer means for calculating each arc length, theta r, of said coil and further for totaling all said arc lengths.
 8. Apparatus as defined by claim 7 wherein said pulser means generates an electrical pulse.
 9. Apparatus as defined by claim 7 wherein said coil radius signal means comprise means for sensing the outside radius of said coil with low pressure air.
 10. Apparatus as defined by claim 7 wherein said coil radius signal means comprise a light source and photoelectrical eye means for sensing the outside radius of said coil.
 11. Apparatus as defined by claim 7 which includes starting means for initiating the operation of said pulser means and said coil radius signal means in response to the start of mandrel rotation.
 12. Apparatus as defined by claim 7 including shear actuated stop means. 